Light Pollution is Probably Messing With Ocean Life

The bright lights of cities have a clear and well-documented effect on urban wildlife. Less clear, though, is if lights from ports, ships, and offshore oil rigs affect marine creatures underwater. A recent study off the coast of Wales says yup, it’s probably happening.

Ocean water is full of tiny larvae from a diverse set of sea creatures. And light is an important cue for guiding where the larvae settle to become adult sea squirts, worms, and sea bristles. In a study published in Biology Letters, scientists left 36 plastic panels in the ocean and exposed to them no light or streetlight-level illumination. Here’s what happened, explains Science:

The artificial lights reduced colonization of the panels by the sea squirt, Botrylloides leachi, and the sea bristle, Plumaluria setacea, filter feeders that dine on nutrients and plankton from the water column and keep coastal ecosystems healthy...But the marine worm Spirobranchus lamarcki was much more abundant on artificially lit panels than on control panels. Overall, the study found that the lights either encouraged or discouraged settlement in 39% of the taxa, or groups of species, living on the panels by the end of the experiment period.

This initial small study hints at something larger: artificial light is probably not a bad thing for every animal. It may harm some creatures, and it may help others. In any case, it likely disrupts the ecosystem that would naturally emerge without it. And that is a complicated tale we’re only just beginning to understand.